pinyin_multi_tone.php

<?php
// 会音乐
$a = [];
$a[0] = ["hui", "kuai"];
$a[1] = ["yin"];
$a[2] = ["le", "yue"];

function arr_product($a, $b)
{
    $b = reset($b);
    $tmp = [];
    foreach ($a as $subA) {
        foreach ($b as $subB) {
            $tmp[] =  $subA . "," . $subB;
        }
    }
    return [$tmp];
}

function combine($a)
{
    if(count($a) > 1) {
        return arr_product(array_shift($a), combine($a));
    } else {
        return $a;
    }
}

var_dump(combine($a)[0]);